Tag Archives: Islands

Researchers have solid proof that the sea is rising — five islands have been lost so far, six more underway in the Solomon Islands

Sea level rise threatens to gulp up coasts and islands in the future; a new study shows that the future is already here in that regard.

A vista from Visale, Solomon Islands.
Image via Wikimedia.

At least five islands in the Solomon Islands chain have been completely lost to rising seas and coastal erosion. These islands have completely vanished under the surface, and the authors note at least two cases where entire human populations have had to relocate to avoid the waves.

This is the first scientific evidence that confirms anecdotal accounts from across the Pacific of the dramatic impacts of climate change on coastlines and communities.

Et tu, Atlantis?

“Using time series aerial and satellite imagery from 1947 to 2014 of 33 islands, along with historical insight from local knowledge, we have identified five vegetated reef islands that have vanished over this time period and a further six islands experiencing severe shoreline recession,” the authors write.

The five lost islands ranged in size from one to five hectares and supported dense tropical vegetation, the study explains. Some of the islands that are in the process of disappearing are inhabited. Nuatambu Island, home to 25 families, has lost more than half of its habitable area (and 11 houses) into the sea since 2011.

The findings are both surprising and worrying, as previous research had estimated that islands in the Pacific can keep pace with sea-level rise, and maybe even expand. However, the team notes that those studies focused on areas of the Pacific where sea levels rise by only 3-5 mm per year – broadly in line with the global average of 3 mm per year. The Solomon Islands have experienced a much more rapid sea level rise over the last two decades, at almost three times the global average.

This higher local rate is partly the result of natural climate variability. However, they’re a good indication of how fast sea levels will rise around the world in a warmer future. While natural variations and geological activity will affect future rates of sea level rise, if we don’t dramatically slash greenhouse emissions, what’s happening in the Solomons right now will become the new normal.

It’s not just that the sea is creeping up — it’s also slowly breaking apart the islands. The team says that rates of coastal erosion in the Solomon Islands are ‘dramatic’ and point to increased wave energy as the likely culprit. Those islands that had to contend with both higher wave energy and sea-level rise fared the worst out of all the islands in the study. Around 12 islands in a low wave-energy area showed very little change in their shorelines, while out of 21 exposed islands 5 disappeared completely and 6 showed substantial levels of erosion.

Twelve islands that were studied in a low wave energy area of Solomon Islands experienced little noticeable change in shorelines despite being exposed to similar sea-level rise. However, of the 21 islands exposed to higher wave energy, five completely disappeared and a further six islands eroded substantially.

The paper “Interactions between sea-level rise and wave exposure on reef island dynamics in the Solomon Islands” has been published in the journal Environmental Research Letters.

Maldives.

Rising seas might mean more coral reef islands — if we don’t murder all the corals

There might be a silver lining to sea level rise — emphasis on ‘might’.

Maldives.

Coral reef rim islands, Huvadhoo Atoll, Republic of Maldives.
Image credits Prof. Paul Kench.

New research proposes that rising sea levels may help the long-term formation of coral reef islands, such as the Maldives. However, all the other bits of climate change may destroy any benefits it brings.

Climate change, island change

“Coral reef islands are typically believed to be highly vulnerable to rising sea levels. This is a major concern for coral reef island nations, in which reef islands provide the only habitable land,” says lead author Dr. Holly East of the Department of Geography and Environmental Sciences at Northumbria University, Newcastle.

Coral reef islands aren’t very keen on altitude; typically, they’re less than three meters (about 10 feet) above the water’s surface. This obviously makes them very vulnerable to rising sea levels. However, the same high seas might’ve also created the islands, the team reports.

The researchers studied five islands in the southern Maldives. By drilling out core samples, they were able to reconstruct when and how the islands formed. They report that storms off the coast of South Africa created a series of large waves (‘high-energy wave events’) that led to the formation of the Maldives. These violent waves dislodged large chunks of pre-existent reefs and transported them onto reef platforms. This stacking of reef material created the foundations of the islands we see today.

“We have found evidence that the Maldivian rim reef islands actually formed under higher sea levels than we have at present,” Dr. East adds.

“This gives us some optimism that if climate change causes rising sea levels and increases in the magnitude of high-energy wave events in the region, it may actually create the perfect conditions to reactivate the processes that built the reef islands in the first place, rather than drowning them.”

The seas were around 0.5 meters (1.5 feet) higher than today during the islands’ formations — this allowed the waves to carry more energy. Both the higher sea level and large wave events were critical to the construction of the islands. Now, (man-made) climate change is also pushing up sea levels; the team says that projected increases in both sea level and the magnitude of large wave events could actually lead to the growth of reef islands.

For that to happen, however, you need living, healthy coral in the region’s reef communities, Dr. East stresses. And we’re murdering them pretty fast right now.

“As these islands are mostly made from coral, a healthy coral reef is vital to provide the materials for island building. However, this could be problematic as corals face a range of threats under climate change, including increasing sea surface temperatures and ocean acidity,” she says.

“If the reef is unhealthy, we could end up with the perfect building conditions but not the bricks.”

She also cautioned that “the large wave events required for reef island building may devastate island infrastructure, potentially compromising the habitability of reef islands in their current form.” Factoring in higher sea levels as well, she says that reef island nations need to “develop infrastructure with the capacity to withstand, or be adaptable to, large wave events” — a task she summarizes as being a “challenge”.

Their paper, “Coral Reef Island Initiation and Development Under Higher Than Present Sea Levels,” has been published in the journal Geophysical Research Letters.